<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
 <HEAD>
  <TITLE>Apache Server Frequently Asked Questions</TITLE>
 </HEAD>

 <!-- Background white, links blue (unvisited), navy (visited), red (active) -->
 <BODY
  BGCOLOR="#FFFFFF"
  TEXT="#000000"
  LINK="#0000FF"
  VLINK="#000080"
  ALINK="#FF0000"
 >
  <!--#include virtual="header.html" -->
  <H1 ALIGN="CENTER">Apache Server Frequently Asked Questions</H1>
  <P>
  $Revision: 1.63.2.14 $ ($Date: 1997/08/03 08:47:57 $)
  </P>
  <P>
  The latest version of this FAQ is always available from the main
  Apache web site, at
  &lt;<A
       HREF="http://www.apache.org/docs/misc/FAQ"
       REL="Help"
      ><SAMP>http://www.apache.org/docs/misc/FAQ</SAMP></A>&gt;.
  </P>
<!-- Notes about changes:                                           -->
<!--  - If adding a relative link to another part of the            -->
<!--    documentation, *do* include the ".html" portion.  There's a -->
<!--    good chance that the user will be reading the documentation -->
<!--    on his own system, which may not be configured for          -->
<!--    multiviews.   Leave off the ".html" extension for absolute  -->
<!--    links to sites which are known to run multiviews (e.g.,     -->
<!--    apache.org or apacheweek.com).                              -->
<!--  - When adding items, make sure they're put in the right place -->
<!--    - verify that the numbering matches up.                     -->
<!--  - *Don't* use <PRE></PRE> blocks - they don't appear          -->
<!--    correctly in a reliable way when this is converted to text  -->
<!--    with Lynx.  Use <DL><DD><CODE>xxx<BR>xx</CODE></DD></DL>    -->
<!--    blocks inside a <P></P> instead.  This is necessary to get  -->
<!--    the horizontal and vertical indenting right.                -->
<!--  - Don't forget to include an HR tag after the last /P tag     -->
<!--    but before the /LI in an item.                              -->
  <P>
  If you are reading a text-only version of this FAQ, you may find numbers
  enclosed in brackets (such as &quot;[12]&quot;).  These refer to the list of
  reference URLs to be found at the end of the document.  These references
  do not appear, and are not needed, for the hypertext version.
  </P>
  <H2>The Questions</H2>
<!-- Stuff to Add:                                                  -->
<!-- - can't bind to port 80                                        -->
<!--   - permission denied                                          -->
<!--   - address already in use                                     -->
<!-- - mod_auth & passwd lines "user:pw:.*" - ++1st colon onward is -->
<!--   treated as pw, not just ++1st to --2nd.                      -->
<!-- - SSL:                                                         -->
<!--   - Can I use Apache-SSL for free in Canada?                   -->
<!--   - Why can't I use Apache-SSL in the U.S.?                    -->
<!-- - How can I found out how many visitors my site gets?          -->
<!-- - How do I add a counter?                                      -->
<!-- - How do I configure Apache as a proxy?                        -->
<!-- - What browsers support HTTP/1.1?                              -->
<!-- - What's the point of vhosts-by-name is there aren't any       -->
<!--   HTTP/1.1 browsers?                                           -->
<!-- - Is there an Apache for W95/WNT?                              -->
<!-- - Why does Apache die when a vhost can't be DNS-resolved?      -->
<!-- - Why do I get "send lost connection" messages in my error     -->
<!--   log?                                                         -->
<!--   - specifically consider .pdf files which seem to cause this  -->
<!--     a lot when accessed via the plugin ... and also mention    -->
<!--     how range-requests can cause bytes served < file size      -->
<!-- - Why do directory indexes appear as garbage?  (A: -lucb)      -->
<!-- - How do I add a footer to all pages offered by my server?     -->
<!-- - Fix midi question; a bigger problem than midi vs. x-midi is  -->
<!--   the simple fact that older versions of Apache (and new ones  -->
<!--   that have been upgraded without upgrading the mime.types     -->
<!--   file) don't have the type listed at all.                     -->
<!-- - Why is my .htaccess ignored?                                 -->
<!-- - RewriteRule /~fraggle/* /cgi-bin/fraggle.pl does not work    -->
<UL>
 <LI><STRONG>Background</STRONG>
  <OL START=1>
   <LI><A HREF="#what">What is Apache?</A>
   </LI>
   <LI><A HREF="#why">Why was Apache created?</A>
   </LI>
   <LI><A HREF="#relate">How does The Apache Group's work relate to
    other servers?</A>
   </LI>
   <LI><A HREF="#name">Why the name &quot;Apache&quot;?</A>
   </LI>
   <LI><A HREF="#compare">OK, so how does Apache compare to other servers?</A>
   </LI>
   <LI><A HREF="#tested">How thoroughly tested is Apache?</A>
   </LI>
   <LI><A HREF="#future">What are the future plans for Apache?</A>
   </LI>
   <LI><A HREF="#support">Whom do I contact for support?</A>
   </LI>
   <LI><A HREF="#more">Is there any more information on Apache?</A>
   </LI>
   <LI><A HREF="#where">Where can I get Apache?</A>
   </LI>
  </OL>
 </LI>
 <LI><STRONG>Technical Questions</STRONG>
  <OL START=11>
   <LI><A HREF="#what2do">&quot;Why can't I ...?  Why won't ...
        work?&quot;  What to do in case of problems</A>
   </LI>
   <LI><A HREF="#compatible">How compatible is Apache with my existing
    NCSA 1.3 setup?</A>
   </LI>
   <LI><A HREF="#CGIoutsideScriptAlias">How do I enable CGI execution
        in directories other than the ScriptAlias?</A>
   </LI>
   <LI><A HREF="#premature-script-headers">What does it mean when my
        CGIs fail with &quot;<SAMP>Premature end of script
        headers</SAMP>&quot;?</A>
   </LI>
   <LI><A HREF="#ssi-part-i">How do I enable SSI (parsed HTML)?</A>
   </LI>
   <LI><A HREF="#ssi-part-ii">Why don't my parsed files get cached?</A>
   </LI>
   <LI><A HREF="#ssi-part-iii">How can I have my script output parsed?</A>
   </LI>
   <LI><A HREF="#proxy">Does or will Apache act as a Proxy server?</A>
   </LI>
   <LI><A HREF="#multiviews">What are &quot;multiviews&quot;?</A>
   </LI>
   <LI><A HREF="#fdlim">Why can't I run more than &lt;<EM>n</EM>&gt;
    virtual hosts?</A>
   </LI>
   <LI><A HREF="#freebsd-setsize">Can I increase FD_SETSIZE on FreeBSD?</A>
   </LI>
   <LI><A HREF="#limitGET">Why do I keep getting &quot;access denied&quot; for
    form POST requests?</A>
   </LI>
   <LI><A HREF="#passwdauth">Can I use my <SAMP>/etc/passwd</SAMP> file
    for Web page authentication?</A>
   </LI>
   <LI><A HREF="#errordoc401">Why doesn't my <CODE>ErrorDocument
    401</CODE> work?</A>
   </LI>
   <LI><A HREF="#setgid">Why do I get &quot;<SAMP>setgid: Invalid
    argument</SAMP>&quot; at startup?</A>
   </LI>
   <LI><A HREF="#cookies1">Why does Apache send a cookie on every response?</A>
   </LI>
   <LI><A HREF="#cookies2">Why don't my cookies work, I even compiled in
    <SAMP>mod_cookies</SAMP>?</A>
   </LI>
   <LI><A HREF="#jdk1-and-http1.1">Why do my Java app[let]s give me plain text
    when I request an URL from an Apache server?</A>
   </LI>
   <LI><A HREF="#putsupport">Why can't I publish to my Apache server
    using PUT on Netscape Gold and other programs?</A>
   </LI>
   <LI><A HREF="#fastcgi">Why isn't FastCGI included with Apache any
    more?</A>
   </LI>
   <LI><A HREF="#nodelay">Why am I getting &quot;<SAMP>httpd: could not
    set socket option TCP_NODELAY</SAMP>&quot; in my error log?</A>
   </LI>
   <LI><A HREF="#peerreset">Why am I getting &quot;<SAMP>connection
    reset by peer</SAMP>&quot; in my error log?</A>
   </LI>
   <LI><A HREF="#nph-scripts">How can I get my script's output without
    Apache buffering it?</A>
   </LI>
   <LI><A HREF="#linuxiovec">Why do I get complaints about redefinition
    of &quot;<CODE>struct iovec</CODE>&quot; when compiling under Linux?</A>
   </LI>
   <LI><A HREF="#wheres-the-dump">The errorlog says Apache dumped core,
    but where's the dump file?</A>
   </LI>
   <LI><A HREF="#dnsauth">Why isn't restricting access by host or domain name
    working correctly?</A>
   </LI>
   <LI><A HREF="#SSL-i">Why doesn't Apache include SSL?</A>
   </LI>
   <LI><A HREF="#HPUX-core">Why do I get core dumps under HPUX using
    HP's ANSI C compiler?</A>
   </LI>
   <LI><A HREF="#midi">How do I get Apache to send a MIDI file so the
    browser can play it?</A>
   </LI>
   <LI><A HREF="#cantbuild">Why won't Apache compile with my
    system's <SAMP>cc</SAMP>?</A>
   </LI>
   <LI><A HREF="#addlog">How do I add browsers and referrers to my
    logs?</A>
   </LI>
   <LI><A HREF="#bind8.1">Why do I get an error about an undefined
    reference to &quot;<SAMP>__inet_ntoa</SAMP>&quot; or other
    <SAMP>__inet_*</SAMP> symbols?</A>
   </LI>
   <LI><A HREF="#set-servername">Why does accessing directories only work
    when I include the trailing "/"
    (<EM>e.g.</EM>,&nbsp;<SAMP>http://foo.domain.com/~user/</SAMP>) but
    not when I omit it
    (<EM>e.g.</EM>,&nbsp;<SAMP>http://foo.domain.com/~user</SAMP>)?</A>
   </LI>
   <LI><A HREF="#user-authentication">How do I set up Apache to require
    a username and password to access certain documents?</A>
   </LI>
   <LI><A HREF="#remote-user-var">Why is the environment variable
   <SAMP>REMOTE_USER</SAMP> not set?</A>
   </LI>
   <LI><A HREF="#remote-auth-only">How do I set up Apache to allow access
    to certain documents only if a site is either a local site
    <EM>or</EM> the user supplies a password and username?</A>
   </LI>
   <LI><A HREF="#no-info-directives">Why doesn't mod_info list any
    directives?</A>
   <LI><A HREF="#linux-shmget">When I run it under Linux I get "shmget:
    function not found", what should I do?</A>
   </LI>
   <LI><A HREF="#authauthoritative">Why does my authentication give
    me a server error?</A>
   <LI><A HREF="#auth-on-same-machine">Do I have to keep the (mSQL)
    authentication information on the same machine?</A>
   </LI>
   <LI><A HREF="#msql-slow">Why is my mSQL authentication terribly slow?</A>
   </LI>
   <LI><A HREF="#rewrite-more-config">Where can I find mod_rewrite rulesets
    which already solve particular URL-related problems?</A>
   </LI>
   <LI><A HREF="#rewrite-article">Where can I find any published information about
    URL-manipulations and mod_rewrite?</A>
   </LI>
   <LI><A HREF="#rewrite-complexity">Why is mod_rewrite so difficult to learn
    and seems so complicated?</A>
   </LI>
   <LI><A HREF="#rewrite-dontwork">What can I do if my RewriteRules don't work
    as expected?</A>
   </LI>
   <LI><A HREF="#rewrite-prefixdocroot">Why don't some of my URLs get
    prefixed with DocumentRoot when using mod_rewrite?</A>
   </LI>
   <LI><A HREF="#rewrite-nocase">How can I make all my URLs case-insensitive
    with mod_rewrite?</A>
   </LI>
   <LI><A HREF="#rewrite-virthost">Why are RewriteRules in my VirtualHost
    parts ignored?</A>
   </LI>
   <LI><A HREF="#rewrite-envwhitespace">How can I use strings with whitespaces
    in RewriteRule's ENV flag?</A>
   </LI>
   <LI><A HREF="#cgi-spec">Where can I find the &quot;CGI
    specification&quot;?</A>
   </LI>
  </OL>
 </LI>
</UL>

<HR>

  <H2>The Answers</H2>
  <H3>
   Background
  </H3>
<OL START=1>
 <LI><A NAME="what">
      <STRONG>What is Apache?</STRONG>
     </A>
  <P>
  Apache was originally based on code and ideas found in the most
  popular HTTP server of the time.. NCSA httpd 1.3 (early 1995). It has
  since evolved into a far superior system which can rival (and probably
  surpass) almost any other UNIX based HTTP server in terms of functionality,
  efficiency and speed.
  </P>
  <P>
  Since it began, it has been completely rewritten, and includes many new
  features. Apache is, as of January 1997, the most popular WWW server on
  the Internet, according to the
  <A
   HREF="http://www.netcraft.com/Survey/"
  >Netcraft Survey</A>.
  </P>
  <HR>
 </LI>
 <LI><A NAME="why">
      <STRONG>Why was Apache created?</STRONG>
     </A>
  <P>
  To address the concerns of a group of WWW providers and part-time httpd
  programmers that httpd didn't behave as they wanted it to behave.
  Apache is an entirely volunteer effort, completely funded by its
  members, not by commercial sales.
  </P>
  <HR>
 </LI>
 <LI><A NAME="relate">
      <STRONG>How does The Apache Group's work relate to other
      server efforts, such as NCSA's?</STRONG>
     </A>
  <P>
  We, of course, owe a great debt to NCSA and their programmers for
  making the server Apache was based on. We now, however, have our own
  server, and our project is mostly our own. The Apache Project is an
  entirely independent venture.
  </P>
  <HR>
 </LI>
 <LI><A NAME="name">
      <STRONG>Why the name &quot;Apache&quot;?</STRONG>
      </A>
  <P>
  A cute name which stuck. Apache is &quot;<STRONG>A
  PA</STRONG>t<STRONG>CH</STRONG>y server&quot;.  It was
  based on some existing code and a series of &quot;patch files&quot;.
  </P>
  <HR>
 </LI>
 <LI><A NAME="compare">
      <STRONG>OK, so how does Apache compare to other servers?</STRONG>
     </A>
  <P>
  For an independent assessment, see
  <A
   HREF="http://webcompare.iworld.com/compare/chart.html"
  >Web Compare</A>'s
  comparison chart.
  </P>
  <P>
  Apache has been shown to be substantially faster than many other
  free servers. Although certain commercial servers have claimed to
  surpass Apache's speed (it has not been demonstrated that any of these
  &quot;benchmarks&quot; are a good way of measuring WWW server speed at any
  rate), we feel that it is better to have a mostly-fast free server
  than an extremely-fast server that costs thousands of dollars. Apache
  is run on sites that get millions of hits per day, and they have
  experienced no performance difficulties.
  </P>
  <HR>
 </LI>
 <LI><A NAME="tested">
      <STRONG>How thoroughly tested is Apache?</STRONG>
     </A>
  <P>
  Apache is run on over 500,000 Internet servers (as of July 1997). It has
  been tested thoroughly by both developers and users. The Apache Group
  maintains rigorous standards before releasing new versions of their
  server, and our server runs without a hitch on over one third of all
  WWW servers available on the Internet.  When bugs do show up, we
  release patches and new versions as soon as they are available.
  </P>
  <P>
  The Apache project's web site includes a page with a partial list of
  <A
   HREF="http://www.apache.org/info/apache_users"
  >sites running Apache</A>.
  </P>
  <HR>
 </LI>
 <LI><A NAME="future">
      <STRONG>What are the future plans for Apache?</STRONG>
     </A>
  <P>
  <UL>
   <LI>to continue as a public domain HTTP server,
   </LI>
   <LI>to keep up with advances in HTTP protocol and web developments in
    general,
   </LI>
   <LI>to collect suggestions for fixes/improvements from its users,
   </LI>
   <LI>to respond to needs of large volume providers as well as
    occasional users.
   </LI>
  </UL>
  </P>
  <HR>
 </LI>
 <LI><A NAME="support">
      <STRONG>Whom do I contact for support?</STRONG>
     </A>
  <P>
  There is no official support for Apache. None of the developers want to
  be swamped by a flood of trivial questions that can be resolved elsewhere.
  Bug reports and suggestions should be sent <EM>via</EM>
  <A
   HREF="http://www.apache.org/bug_report"
  >the bug report page</A>.
  Other questions should be directed to the
  <A
   HREF="news:comp.infosystems.www.servers.unix"
  ><SAMP>comp.infosystems.www.servers.unix</SAMP></A>
  newsgroup, where some of the Apache team lurk,
  in the company of many other httpd gurus who should be able
  to help.
  </P>
  <P>
  Commercial support for Apache is, however, available from a number
  of third parties.
  </P>
  <HR>
 </LI>
 <LI><A NAME="more">
      <STRONG>Is there any more information available on
      Apache?</STRONG>
     </A>
  <P>
  Indeed there is.  See the main
  <A
   HREF="http://www.apache.org/"
  >Apache web site</A>.
  There is also a regular electronic publication called
  <A
   HREF="http://www.apacheweek.com/"
   REL="Help"
  ><CITE>Apache Week</CITE></A>
  available.  Links to relevant <CITE>Apache Week</CITE> articles are
  included below where appropriate.
  </P>
  <HR>
 </LI>
 <LI><A NAME="where">
      <STRONG>Where can I get Apache?</STRONG>
     </A>
  <P>
  You can find out how to download the source for Apache at the
  project's
  <A
   HREF="http://www.apache.org/"
  >main web page</A>.
  </P>
  <HR>
 </LI>
</OL>
  <H3>
   Technical Questions
  </H3>
<OL START=11>
 <LI><A NAME="what2do">
      <STRONG>&quot;Why can't I ...?  Why won't ... work?&quot;  What to
      do in case of problems</STRONG>
     </A>
  <P>
  If you are having trouble with your Apache server software, you should
  take the following steps:
  </P>
  <OL>
   <LI><STRONG>Check the errorlog!</STRONG>
    <P>
    Apache tries to be helpful when it encounters a problem.  In many
    cases, it will provide some details by writing one or messages to
    the server error log.  Sometimes this is enough for you to diagnose
    &amp; fix the problem yourself (such as file permissions or the like).
    The default location of the error log is
    <SAMP>/usr/local/etc/httpd/logs/error_log</SAMP>, but see the
    <A
     HREF="../mod/core.html#errorlog"
    ><SAMP>ErrorLog</SAMP></A>
    directive in your config files for the location on your server.
    </P>
   </LI>
   <LI><STRONG>Check the
    <A
     HREF="http://www.apache.org/docs/misc/FAQ.html"
    >FAQ</A>!</STRONG>
    <P>
    The latest version of the Apache Frequently-Asked Questions list can
    always be found at the main Apache web site.
    </P>
   </LI>
   <LI><STRONG>Check the Apache bug database</STRONG>
    <P>
    Most problems that get reported to The Apache Group are recorded in
    the
    <A
     HREF="http://www.apache.org/bugdb.cgi"
    >bug database</A>.
    <EM><STRONG>Please</STRONG> check the existing reports, open
    <STRONG>and</STRONG> closed, before adding one.</EM>  If you find
    that your issue has already been reported, please <EM>don't</EM> add
    a &quot;me, too&quot; report.  If the original report isn't closed
    yet, we suggest that you check it periodically.  You might also
    consider contacting the original submitter, because there may be an
    email exchange going on about the issue that isn't getting recorded
    in the database.
    </P>
   </LI>
   <LI><STRONG>Ask in the <SAMP>comp.infosystems.www.servers.unix</SAMP>
    USENET newsgroup</STRONG>
    <P>
    A lot of common problems never make it to the bug database because
    there's already high Q&amp;A traffic about them in the
    <A
     HREF="news:comp.infosystems.www.servers.unix"
    ><SAMP>comp.infosystems.www.servers.unix</SAMP></A>
    newsgroup.  Many Apache users, and some of the developers, can be
    found roaming its virtual halls, so it is suggested that you seek
    wisdom there.  The chances are good that you'll get a faster answer
    there than from the bug database, even if you <EM>don't</EM> see
    your question already posted.
    </P>
   </LI>
   <LI><STRONG>If all else fails, report the problem in the bug
    database</STRONG>
    <P>
    If you've gone through those steps above that are appropriate and
    have obtained no relief, then please <EM>do</EM> let The Apache
    Group know about the problem by
    <A
     HREF="http://www.apache.org/bugdb.cgi"
    >logging a bug report</A>.
    </P>
    <P>
    If your problem involves the server crashing and generating a core
    dump, please include a backtrace (if possible).  As an example,
    </P>
    <P>
    <DL>
     <DD><CODE># cd <EM>ServerRoot</EM><BR>
      # dbx httpd core<BR>
      (dbx) where</CODE>
     </DD>
    </DL>
    </P>
    <P>
    (Substitute the appropriate locations for your
    <SAMP>ServerRoot</SAMP> and your <SAMP>httpd</SAMP> and
    <SAMP>core</SAMP> files.  You may have to use <CODE>gdb</CODE>
    instead of <CODE>dbx</CODE>.)
    </P>
   </LI>
  </OL>
  <HR>
 </LI>
 <LI><A NAME="compatible">
      <STRONG>How compatible is Apache with my existing NCSA 1.3
      setup?</STRONG>
     </A>
  <P>
  Apache attempts to offer all the features and configuration options
  of NCSA httpd 1.3, as well as many of the additional features found in
  NCSA httpd 1.4 and NCSA httpd 1.5.
  </P>
  <P>
  NCSA httpd appears to be moving toward adding experimental features
  which are not generally required at the moment. Some of the experiments
  will succeed while others will inevitably be dropped. The Apache
  philosophy is to add what's needed as and when it is needed.
  </P>
  <P>
  Friendly interaction between Apache and NCSA developers should ensure
  that fundamental feature enhancements stay consistent between the two
  servers for the foreseeable future.
  </P>
  <HR>
 </LI>
 <LI><A NAME="CGIoutsideScriptAlias">
      <STRONG>How do I enable CGI execution in directories other than
      the ScriptAlias?</STRONG>
     </A>
  <P>
  Apache recognizes all files in a directory named as a
  <A
   HREF="../mod/mod_alias.html#scriptalias"
  ><SAMP>ScriptAlias</SAMP></A>
  as being eligible for execution rather than processing as normal
  documents.  This applies regardless of the file name, so scripts in a
  ScriptAlias directory don't need to be named
  &quot;<SAMP>*.cgi</SAMP>&quot; or &quot;<SAMP>*.pl</SAMP>&quot; or
  whatever.  In other words, <EM>all</EM> files in a ScriptAlias
  directory are scripts, as far as Apache is concerned.
  </P>
  <P>
  To persuade Apache to execute scripts in other locations, such as in
  directories where normal documents may also live, you must tell it how
  to recognize them - and also that it's okay to execute them.  For
  this, you need to use something like the
  <A
   HREF="../mod/mod_mime.html#addhandler"
  ><SAMP>AddHandler</SAMP></A>
  directive.
  </P>
  <P>
  <OL>
   <LI>In an appropriate section of your server configuration files, add
    a line such as
    <P>
    <DL>
     <DD><CODE>AddHandler cgi-script .cgi</CODE>
     </DD>
    </DL>
    </P>
    <P>
    The server will then recognize that all files in that location (and
    its logical descendants) that end in &quot;<SAMP>.cgi</SAMP>&quot;
    are script files, not documents.
    </P>
   </LI>
   <LI>Make sure that the directory location is covered by an
    <A
     HREF="../mod/core.html#options"
    ><SAMP>Options</SAMP></A>
    declaration that includes the <SAMP>ExecCGI</SAMP> option.
   </LI>
  </OL>
  </P>
  <P>
  In some situations it can be not conform to your local policy to actually
  allow all files named &quot;<SAMP>*.cgi</SAMP>&quot; to be executable.
  Perhaps all you want is to enable a particular file in a normal directory to
  be executable. This can be alternatively accomplished 
  via 
  <A
   HREF="../mod/mod_rewrite.html"
  ><SAMP>mod_rewrite</SAMP></A> 
  and the following steps:
  </P>
  <P>
  <OL>
   <LI>Locally add to the corresponding <SAMP>.htaccess</SAMP> file a ruleset
       similar to this one:
    <P>
    <DL>
     <DD><CODE>RewriteEngine on
      <BR>
      RewriteBase   /~foo/bar/
      <BR>
      RewriteRule   ^quux\.cgi$  -  [T=application/x-httpd-cgi]</CODE>
     </DD>
    </DL>
    </P>
   </LI>
   <LI>Make sure that the directory location is covered by an
    <A
     HREF="../mod/core.html#options"
    ><SAMP>Options</SAMP></A>
        declaration that includes the <SAMP>ExecCGI</SAMP> and
        <SAMP>FollowSymLinks</SAMP> option.
   </LI>
  </OL>
  </P>
  <HR>
 </LI>
 <LI><A NAME="premature-script-headers">
      <STRONG>What does it mean when my CGIs fail with
      &quot;<SAMP>Premature end of script headers</SAMP>&quot;?</STRONG>
     </A>
  <P>
  It means just what it says: the server was expecting a complete set of
  HTTP headers (one or more followed by a blank line), and didn't get
  them.
  </P>
  <P>
  The most common cause of this problem is the script dying before
  sending the complete set of headers, or possibly any at all, to the
  server.  To see if this is the case, try running the script standalone
  from an interactive session, rather than as a script under the server.
  If you get error messages, this is almost certainly the cause of the
  &quot;premature end of script headers&quot; message.
  </P>
  <P>
  The second most common cause of this (aside from people not
  outputting the required headers at all) is a result of an interaction
  with Perl's output buffering.  To make Perl flush its buffers
  after each output statement, insert the following statements around
  the <CODE>print</CODE> or <CODE>write</CODE> statements that send your
  HTTP headers:
  </P>
  <P>
  <DL>
   <DD><CODE>{<BR>
    &nbsp;local ($oldbar) = $|;<BR>
    &nbsp;$cfh = select (STDOUT);<BR>
    &nbsp;$| = 1;<BR>
    &nbsp;#<BR>
    &nbsp;# print your HTTP headers here<BR>
    &nbsp;#<BR>
    &nbsp;$| = $oldbar;<BR>
    &nbsp;select ($cfh);<BR>
    }</CODE>
   </DD>
  </DL>
  </P>
  <P>
  This is generally only necessary when you are calling external
  programs from your script that send output to stdout, or if there will
  be a long delay between the time the headers are sent and the actual
  content starts being emitted.  To maximize performance, you should
  turn buffer-flushing back <EM>off</EM> (with <CODE>$| = 0</CODE> or the
  equivalent) after the statements that send the headers, as displayed
  above.
  </P>
  <P>
  If your script isn't written in Perl, do the equivalent thing for
  whatever language you <EM>are</EM> using (<EM>e.g.</EM>, for C, call
  <CODE>fflush()</CODE> after writing the headers).
  </P>
  <HR>
 </LI>
 <LI><A NAME="ssi-part-i">
      <STRONG>How do I enable SSI (parsed HTML)?</STRONG>
     </A>
  <P>
  SSI (an acronym for Server-Side Include) directives allow static HTML
  documents to be enhanced at run-time (<EM>e.g.</EM>, when delivered to
  a client by Apache).  The format of SSI directives is covered
  in the <A HREF="../mod/mod_include.html">mod_include manual</A>;
  suffice it to say that Apache supports not only SSI but
  xSSI (eXtended SSI) directives.
  </P>
  <P>
  Processing a document at run-time is called <EM>parsing</EM> it; hence
  the term &quot;parsed HTML&quot; sometimes used for documents that
  contain SSI instructions.  Parsing tends to be <EM>extremely</EM>
  resource-consumptive, and is not enabled by default.  It can also
  interfere with the cachability of your documents, which can put a
  further load on your server.  (see the
  <A
   HREF="#ssi-part-ii"
  >next question</A>
  for more information about this.)
  </P>
  <P>
  To enable SSI processing, you need to
  </P>
  <UL>
   <LI>Build your server with the
    <A
     HREF="../mod/mod_include.html"
    ><SAMP>mod_include</SAMP></A>
    module.  This is normally compiled in by default.
   </LI>
   <LI>Make sure your server configuration files have an
    <A
     HREF="../mod/core.html#options"
    ><SAMP>Options</SAMP></A>
    directive which permits <SAMP>Includes</SAMP>.
   </LI>
   <LI>Make sure that the directory where you want the SSI documents to
    live is covered by the &quot;server-parsed&quot; content handler,
    either explicitly or in some ancestral location.  That can be done
    with the following
    <A
     HREF="../mod/mod_mime.html#addhandler"
    ><SAMP>AddHandler</SAMP></A>
    directive:
    <P>
    <DL>
     <DD><CODE>AddHandler server-parsed .shtml</CODE>
     </DD>
    </DL>
    </P>
    This indicates that all files ending in &quot;.shtml&quot; in that
    location (or its descendants) should be parsed.  Note that using
    &quot;.html&quot; will cause all normal HTML files to be parsed,
    which may put an inordinate load on your server.
   </LI>
  </UL>
  <P>
  For additional information, see the <CITE>Apache Week</CITE> article
  on
  <A
   HREF="http://www.apacheweek.com/features/ssi"
   REL="Help"
  ><CITE>Using Server Side Includes</CITE></A>.
  </P>
  <HR>
 </LI>
 <LI><A NAME="ssi-part-ii">
      <STRONG>Why don't my parsed files get cached?</STRONG>
     </A>
  <P>
  Since the server is performing run-time processing of your SSI
  directives, which may change the content shipped to the client, it
  can't know at the time it starts parsing what the final size of the
  result will be, or whether the parsed result will always be the same.
  This means that it can't generate <SAMP>Content-Length</SAMP> or
  <SAMP>Last-Modified</SAMP> headers.  Caches commonly work by comparing
  the <SAMP>Last-Modified</SAMP> of what's in the cache with that being
  delivered by the server.  Since the server isn't sending that header
  for a parsed document, whatever's doing the caching can't tell whether
  the document has changed or not - and so fetches it again to be on the
  safe side.
  </P>
  <P>
  You can work around this in some cases by causing an
  <SAMP>Expires</SAMP> header to be generated.  (See the
  <A
   HREF="../mod/mod_expires.html"
   REL="Help"
  ><SAMP>mod_expires</SAMP></A>
  documentation for more details.)  Another possibility is to use the
  <A
   HREF="../mod/mod_include.html#xbithack"
   REL="Help"
  ><SAMP>XBitHack Full</SAMP></A>
  mechanism, which tells Apache to send (under certain circumstances
  detailed in the XBitHack directive description) a
  <SAMP>Last-Modified</SAMP> header based upon the last modification
  time of the file being parsed.  Note that this may actually be lying
  to the client if the parsed file doesn't change but the SSI-inserted
  content does; if the included content changes often, this can result
  in stale copies being cached.
  </P>
  <HR>
 </LI>
 <LI><A NAME="ssi-part-iii">
      <STRONG>How can I have my script output parsed?</STRONG>
     </A>
  <P>
  So you want to include SSI directives in the output from your CGI
  script, but can't figure out how to do it?
  The short answer is &quot;you can't.&quot;  This is potentially
  a security liability and, more importantly, it can not be cleanly
  implemented under the current server API.  The best workaround
  is for your script itself to do what the SSIs would be doing.
  After all, it's generating the rest of the content.
  </P>
  <P>
  This is a feature The Apache Group hopes to add in the next major
  release after 1.2.
  </P>
  <HR>
 </LI>
 <LI><A NAME="proxy">
      <STRONG>Does or will Apache act as a Proxy server?</STRONG>
     </A>
  <P>
  Apache version 1.1 and above comes with a
  <A
   HREF="../mod/mod_proxy.html"
  >proxy module</A>.
  If compiled
  in, this will make Apache act as a caching-proxy server.
  </P>
  <HR>
 </LI>
 <LI><A NAME="multiviews">
      <STRONG>What are &quot;multiviews&quot;?</STRONG>
     </A>
  <P>
  &quot;Multiviews&quot; is the general name given to the Apache
  server's ability to provide language-specific document variants in
  response to a request.  This is documented quite thoroughly in the
  <A
   HREF="../content-negotiation.html"
   REL="Help"
  >content negotiation</A>
  description page.  In addition, <CITE>Apache Week</CITE> carried an
  article on this subject entitled
  &quot;<A
         HREF="http://www.apacheweek.com/features/negotiation"
         REL="Help"
        ><CITE>Content Negotiation Explained</CITE></A>&quot;.
  </P>
  <HR>
 </LI>
 <LI><A NAME="fdlim">
      <STRONG>Why can't I run more than &lt;<EM>n</EM>&gt;
      virtual hosts?</STRONG>
     </A>
  <P>
  You are probably running into resource limitations in your
  operating system.  The most common limitation is the
  <EM>per</EM>-process limit on <STRONG>file descriptors</STRONG>,
  which is almost always the cause of problems seen when adding
  virtual hosts.  Apache often does not give an intuitive error
  message because it is normally some library routine (such as
  <CODE>gethostbyname()</CODE>) which needs file descriptors and
  doesn't complain intelligibly when it can't get them.
  </P>
  <P>
  Each log file requires a file descriptor, which means that if you are
  using separate access and error logs for each virtual host, each
  virtual host needs two file descriptors.  Each
  <A
   HREF="../mod/core.html#listen"
  ><SAMP>Listen</SAMP></A>
  directive also needs a file descriptor.
  </P>
  <P>
  Typical values for &lt;<EM>n</EM>&gt; that we've seen are in
  the neighborhood of 128 or 250.  When the server bumps into the file
  descriptor limit, it may dump core with a SIGSEGV, it might just
  hang, or it may limp along and you'll see (possibly meaningful) errors
  in the error log.  One common problem that occurs when you run into
  a file descriptor limit is that CGI scripts stop being executed
  properly.
  </P>
  <P>
  As to what you can do about this:
  </P>
  <OL>
   <LI>Reduce the number of
       <A
        HREF="../mod/core.html#listen"
       ><SAMP>Listen</SAMP></A>
       directives.  If there are no other servers running on the machine
       on the same port then you normally don't
       need any Listen directives at all.  By default Apache listens to
       all addresses on port 80.
   </LI>
   <LI>Reduce the number of log files.  You can use
       <A
        HREF="../mod/mod_log_config.html"
       ><SAMP>mod_log_config</SAMP></A>
       to log all requests to a single log file while including the name
       of the virtual host in the log file.  You can then write a
       script to split the logfile into separate files later if
       necessary.
   </LI>
   <LI>Increase the number of file descriptors available to the server
       (see your system's documentation on the <CODE>limit</CODE> or
       <CODE>ulimit</CODE> commands).  For some systems, information on
       how to do this is available in the
       <A
        HREF="perf.html"
       >performance hints</A>
       page.  There is a specific note for
       <A HREF="#freebsd-setsize">FreeBSD</A> below.
   </LI>
   <LI>&quot;Don't do that&quot; - try to run with fewer virtual hosts
   </LI>
   <LI>Spread your operation across multiple server processes (using
    <A
     HREF="../mod/core.html#listen"
    ><SAMP>Listen</SAMP></A>
    for example, but see the first point) and/or ports.
   </LI>
  </OL>
  <P>
  Since this is an operating-system limitation, there's not much else
  available in the way of solutions.
  </P>
  <P>
  As of 1.2.1 we have made attempts to work around various limitations
  involving running with many descriptors.
  <A HREF="descriptors.html">More information is available.</A>
  </P>
  <HR>
 </LI>

 <LI><A NAME="freebsd-setsize">
      <STRONG>Can I increase <SAMP>FD_SETSIZE</SAMP> on FreeBSD?</STRONG>
     </A>
  <P>
  On versions of FreeBSD before 3.0, the <SAMP>FD_SETSIZE</SAMP> define 
  defaults to 256.  This means that you will have trouble usefully using
  more than 256 file descriptors in Apache.  This can be increased, but
  doing so can be tricky.

  If you are using a version prior to 2.2, you need to recompile your
  kernel with a larger FD_SETSIZE.  This can be done by adding a 
  line such as:
  </P>
  <DL>
   <DD><CODE>options FD_SETSIZE <EM>nnn</EM></CODE>
   </DD>
  </DL>
  <P>
  To your kernel config file.  Starting at version 2.2, this is no
  longer necessary.
  </P>
  <P>
  If you are using a version of 2.1-stable from after 1997/03/10 or
  2.2 or 3.0-current from before 1997/06/28, there is a limit in
  the resolver library that prevents it from using more file descriptors
  than what FD_SETSIZE is set to when libc is compiled.  To increase
  this, you have to recompile libc with a higher FD_SETSIZE.
  </P>
  <P>
  In FreeBSD 3.0, the default FD_SETSIZE has been increased to
  1024 and the above limitation in the resolver library
  has been removed.
  </P>
  <P>
  After you deal with the appropriate changes above, you can increase 
  the setting of <SAMP>FD_SETSIZE</SAMP> at Apache compilation time 
  by adding &quot;<SAMP>-DFD_SETSIZE=<EM>nnn</EM></SAMP>&quot; to the
  <SAMP>EXTRA_CFLAGS</SAMP> line in your <SAMP>Configuration</SAMP>
  file.
  </P>
  <HR>
 </LI>

 <LI><A NAME="limitGET">
      <STRONG>Why do I keep getting &quot;access denied&quot; for form POST
      requests?</STRONG>
     </A>
  <P>
  The most common cause of this is a <SAMP>&lt;Limit&gt;</SAMP> section
  that only names the <SAMP>GET</SAMP> method.  Look in your
  configuration files for something that resembles the following and
  would affect the location where the POST-handling script resides:
  </P>
  <P>
  <DL>
   <DD><CODE>&lt;Limit GET&gt;<BR>&nbsp;&nbsp;&nbsp;&nbsp;:</CODE>
   </DD>
  </DL>
  </P>
  <P>
  Change that to <CODE>&lt;Limit GET POST&gt;</CODE> and the problem
  will probably go away.
  </P>
  <HR>
 </LI>
 <LI><A NAME="passwdauth">
      <STRONG>Can I use my <SAMP>/etc/passwd</SAMP> file
      for Web page authentication?</STRONG>
     </A>
  <P>
  Yes, you can - but it's a <STRONG>very bad idea</STRONG>.  Here are
  some of the reasons:
  </P>
  <UL>
   <LI>The Web technology provides no governors on how often or how
    rapidly password (authentication failure) retries can be made.  That
    means that someone can hammer away at your system's
    <SAMP>root</SAMP> password using the Web, using a dictionary or
    similar mass attack, just as fast as the wire and your server can
    handle the requests.  Most operating systems these days include
    attack detection (such as <EM>n</EM> failed passwords for the same
    account within <EM>m</EM> seconds) and evasion (breaking the
    connection, disabling the account under attack, disabling
    <EM>all</EM> logins from that source, <EM>et cetera</EM>), but the
    Web does not.
   </LI>
   <LI>An account under attack isn't notified (unless the server is
    heavily modified); there's no &quot;You have 19483 login
    failures&quot; message when the legitimate owner logs in.
   </LI>
   <LI>Without an exhaustive and error-prone examination of the server
    logs, you can't tell whether an account has been compromised.
    Detecting that an attack has occurred, or is in progress, is fairly
    obvious, though - <EM>if</EM> you look at the logs.
   </LI>
   <LI>Web authentication passwords (at least for Basic authentication)
    generally fly across the wire, and through intermediate proxy
    systems, in what amounts to plain text.  &quot;O'er the net we
    go/Caching all the way;/O what fun it is to surf/Giving my password
    away!&quot;
   </LI>
   <LI>Since HTTP is stateless, information about the authentication is
    transmitted <EM>each and every time</EM> a request is made to the
    server.  Essentially, the client caches it after the first
    successful access, and transmits it without asking for all
    subsequent requests to the same server.
   </LI>
   <LI>It's relatively trivial for someone on your system to put up a
    page that will steal the cached password from a client's cache
    without them knowing.  Can you say &quot;password grabber&quot;?
   </LI>
  </UL>
  <P>
  If you still want to do this in light of the above disadvantages, the
  method is left as an exercise for the reader.  It'll void your Apache
  warranty, though, and you'll lose all accumulated UNIX guru points.
  </P>
  <HR>
 </LI>
 <LI><A NAME="errordoc401">
      <STRONG>Why doesn't my <CODE>ErrorDocument 401</CODE> work?</STRONG>
     </A>
  <P>
  You need to use it with a URL in the form
  &quot;<SAMP>/foo/bar</SAMP>&quot; and not one with a method and
  hostname such as &quot;<SAMP>http://host/foo/bar</SAMP>&quot;.  See the
  <A
   HREF="../mod/core.html#errordocument"
  ><SAMP>ErrorDocument</SAMP></A>
  documentation for details.  This was incorrectly documented in the past.
  </P>
  <HR>
 </LI>
 <LI><A NAME="setgid">
      <STRONG>Why do I get &quot;<SAMP>setgid: Invalid
      argument</SAMP>&quot; at startup?</STRONG>
     </A>
  <P>
  Your
  <A
   HREF="../mod/core.html#group"
  ><SAMP>Group</SAMP></A>
  directive (probably in <SAMP>conf/httpd.conf</SAMP>) needs to name a
  group that actually exists in the <SAMP>/etc/group</SAMP> file (or
  your system's equivalent).
  </P>
  <HR>
 </LI>
 <LI><A NAME="cookies1">
      <STRONG>Why does Apache send a cookie on every response?</STRONG>
     </A>
  <P>
  Apache does <EM>not</EM> send automatically send a cookie on every
  response, unless you have re-compiled it with the
  <A
   HREF="../mod/mod_cookies.html"
  ><SAMP>mod_cookies</SAMP></A>
  module.
  This module was distributed with Apache prior to 1.2.
  This module may help track users, and uses cookies to do this. If
  you are not using the data generated by <SAMP>mod_cookies</SAMP>, do
  not compile it into Apache. Note that in 1.2 this module was renamed
  to the more correct name
  <A
   HREF="../mod/mod_usertrack.html"
  ><SAMP>mod_usertrack</SAMP></A>,
  and cookies
  have to be specifically enabled with the
  <A
    HREF="../mod/mod_usertrack.html#cookietracking"
  ><SAMP>CookieTracking</SAMP></A>
  directive.
  </P>
  <HR>
 </LI>
 <LI><A NAME="cookies2">
      <STRONG>Why don't my cookies work, I even compiled in
      <SAMP>mod_cookies</SAMP>?
      </STRONG>
     </A>
  <P>
  Firstly, you do <EM>not</EM> need to compile in
  <SAMP>mod_cookies</SAMP> in order for your scripts to work (see the
  <A
   HREF="#cookies1"
  >previous question</A>
  for more about <SAMP>mod_cookies</SAMP>). Apache passes on your
  <SAMP>Set-Cookie</SAMP> header fine, with or without this module. If
  cookies do not work it will be because your script does not work
  properly or your browser does not use cookies or is not set-up to
  accept them.
  </P>
  <HR>
 </LI>
 <LI><A NAME="jdk1-and-http1.1">
      <STRONG>Why do my Java app[let]s give me plain text when I request
      an URL from an Apache server?</STRONG>
     </A>
  <P>
  As of version 1.2, Apache is an HTTP/1.1 (HyperText Transfer Protocol
  version 1.1) server.  This fact is reflected in the protocol version
  that's included in the response headers sent to a client when
  processing a request.  Unfortunately, low-level Web access classes
  included in the Java Development Kit (JDK) version 1.0.2 expect to see
  the version string &quot;HTTP/1.0&quot; and do not correctly interpret
  the &quot;HTTP/1.1&quot; value Apache is sending (this part of the
  response is a declaration of what the server can do rather than a
  declaration of the dialect of the response).  The result
  is that the JDK methods do not correctly parse the headers, and
  include them with the document content by mistake.
  </P>
  <P>
  This is definitely a bug in the JDK 1.0.2 foundation classes from Sun,
  and it has been fixed in version 1.1.  However, the classes in
  question are part of the virtual machine environment, which means
  they're part of the Web browser (if Java-enabled) or the Java
  environment on the client system - so even if you develop
  <EM>your</EM> classes with a recent JDK, the eventual users might
  encounter the problem.
  The classes involved are replaceable by vendors implementing the
  Java virtual machine environment, and so even those that are based
  upon the 1.0.2 version may not have this problem.
  </P>
  <P>
  In the meantime, a workaround is to tell
  Apache to &quot;fake&quot; an HTTP/1.0 response to requests that come
  from the JDK methods; this can be done by including a line such as the
  following in your server configuration files:
  </P>
  <P>
  <DL>
   <DD><CODE>BrowserMatch Java1.0 force-response-1.0
    <BR>
    BrowserMatch JDK/1.0 force-response-1.0</CODE>
   </DD>
  </DL>
  </P>
  <P>
  More information about this issue can be found in the
  <A
   HREF="http://www.apache.org/info/jdk-102"
  ><CITE>Java and HTTP/1.1</CITE></A>
  page at the Apache web site.
  </P>
  <HR>
 </LI>
 <LI><A NAME="putsupport">
      <STRONG>Why can't I publish to my Apache server using PUT on
      Netscape Gold and other programs?</STRONG>
     </A>
  <P>
  Because you need to install and configure a script to handle
  the uploaded files.  This script is often called a &quot;PUT&quot; handler.
  There are several available, but they may have security problems.
  Using FTP uploads may be easier and more secure, at least for now.
  For more information, see the <CITE>Apache Week</CITE> article
  <A
   HREF="http://www.apacheweek.com/features/put"
  ><CITE>Publishing Pages with PUT</CITE></A>.
  </P>
  <HR>
 </LI>
 <LI><A NAME="fastcgi">
      <STRONG>Why isn't FastCGI included with Apache any more?</STRONG>
     </A>
  <P>
  The simple answer is that it was becoming too difficult to keep the
  version being included with Apache synchronized with the master copy
  at the
  <A
   HREF="http://www.fastcgi.com/servers/apache/"
  >FastCGI web site</A>.  When a new version of Apache was released, the
  version of the FastCGI module included with it would soon be out of date.
  </P>
  <P>
  You can still obtain the FastCGI module for Apache from the master
  FastCGI web site.
  </P>
  <HR>
 </LI>
 <LI><A NAME="nodelay">
      <STRONG>Why am I getting &quot;<SAMP>httpd: could not set socket
      option TCP_NODELAY</SAMP>&quot; in my error log?</STRONG>
     </A>
  <P>
  This message almost always indicates that the client disconnected
  before Apache reached the point of calling <CODE>setsockopt()</CODE>
  for the connection.  It shouldn't occur for more than about 1% of the
  requests your server handles, and it's advisory only in any case.
  </P>
  <HR>
 </LI>
 <LI><A NAME="peerreset">
      <STRONG>Why am I getting &quot;<SAMP>connection reset by
      peer</SAMP>&quot; in my error log?</STRONG>
     </A>
  <P>
  This is a normal message and nothing about which to be alarmed.  It simply
  means that the client canceled the connection before it had been
  completely set up - such as by the end-user pressing the &quot;Stop&quot;
  button.  People's patience being what it is, sites with response-time
  problems or slow network links may experiences this more than
  high-capacity ones or those with large pipes to the network.
  </P>
  <HR>
 </LI>
 <LI><A NAME="nph-scripts">
      <STRONG>How can I get my script's output without Apache buffering
      it?</STRONG>
     </A>
  <P>
  In order to improve network performance, Apache buffers script output
  into relatively large chunks.  If you have a script that sends
  information in bursts (such as partial-done messages in a multi-commit
  database transaction, perhaps), the client will not necessarily get
  the output as the script is generating it.
  </P>
  <P>
  To avoid this, Apache recognizes scripts whose names begin with
  &quot;<SAMP>nph-</SAMP>&quot; as <EM>non-parsed-header</EM> scripts.
  That is, Apache won't buffer their output, but connect it directly to
  the socket going back to the client.
  </P>
  <P>
  While this will probably do what you want, there <EM>are</EM> some
  disadvantages to it:
  </P>
  <UL>
   <LI><STRONG>YOU</STRONG> (the script) are responsible for generating
     <STRONG>ALL</STRONG> of the HTTP headers, and no longer
     <EM>just</EM> the &quot;<SAMP>Content-type</SAMP>&quot; or
     &quot;<SAMP>Location</SAMP>&quot; headers
   </LI>
   <LI>Unless your script generates its output carefully, you will see a
    performance penalty as excessive numbers of packets go back and forth
   </LI>
  </UL>
  <P>
  As an example how you might handle the former (in a Perl script):
  </P>
  <P>
  <DL>
   <DD><CODE>if ($0 =~ m:^(.*/)*nph-[^/]*$:) {
    <BR>
    &nbsp;&nbsp;&nbsp;&nbsp;
    $HTTP_headers&nbsp;=&nbsp;
    &quot;HTTP/1.1&nbsp;200&nbsp;OK\015\012&quot;;
    <BR>
    &nbsp;&nbsp;&nbsp;&nbsp;
    $HTTP_headers&nbsp;.=&nbsp;
    &quot;Connection:&nbsp;close\015\012&quot;;
    <BR>
    &nbsp;&nbsp;&nbsp;&nbsp;
    print&nbsp;$HTTP_headers;
    <BR>
    }</CODE>
   </DD>
  </DL>
  </P>
  <P>
  and then follow with your normal non-<SAMP>nph</SAMP> headers.
  </P>
  <HR>
 </LI>
 <LI><A NAME="linuxiovec">
      <STRONG>Why do I get complaints about redefinition
      of &quot;<CODE>struct iovec</CODE>&quot; when
      compiling under Linux?</STRONG>
     </A>
  <P>
  This is a conflict between your C library includes and your kernel
  includes.  You need to make sure that the versions of both are matched
  properly.  There are two workarounds, either one will solve the problem:
  </P>
  <P>
  <UL>
   <LI>Remove the definition of <CODE>struct iovec</CODE> from your C
    library includes.  It is located in <CODE>/usr/include/sys/uio.h</CODE>.
    <STRONG>Or,</STRONG>
   </LI>
   <LI>Add  <CODE>-DNO_WRITEV</CODE> to the <CODE>EXTRA_CFLAGS</CODE>
    line in your <SAMP>Configuration</SAMP> and reconfigure/rebuild.
    This hurts performance and should only be used as a last resort.
   </LI>
  </UL>
  </P>
  <HR>
 </LI>
 <LI><A NAME="wheres-the-dump">
      <STRONG>The errorlog says Apache dumped core, but where's the dump
      file?</STRONG>
     </A>
  <P>
  In Apache version 1.2, the error log message
  about dumped core includes the directory where the dump file should be
  located.  However, many Unixes do not allow a process that has
  called <CODE>setuid()</CODE> to dump core for security reasons;
  the typical Apache setup has the server started as root to bind to
  port 80, after which it changes UIDs to a non-privileged user to
  serve requests.
  </P>
  <P>
  Dealing with this is extremely operating system-specific, and may
  require rebuilding your system kernel.  Consult your operating system
  documentation or vendor for more information about whether your system
  does this and how to bypass it.  If there <EM>is</EM> a documented way
  of bypassing it, it is recommended that you bypass it only for the
  <SAMP>httpd</SAMP> server process if possible.
  </P>
  <P>
  The canonical location for Apache's core-dump files is the
  <A
   HREF="../mod/core.html#serverroot"
  >ServerRoot</A>
  directory.
  </P>
  <HR>
 </LI>
 <LI><A NAME="dnsauth">
      <STRONG>Why isn't restricting access by host or domain name
      working correctly?</STRONG>
     </A>
  <P>
  Two of the most common causes of this are:
  </P>
  <OL>
   <LI><STRONG>An error, inconsistency, or unexpected mapping in the DNS
    registration</STRONG>
    <BR>
    This happens frequently: your configuration restricts access to
    <SAMP>Host.FooBar.Com</SAMP>, but you can't get in from that host.
    The usual reason for this is that <SAMP>Host.FooBar.Com</SAMP> is
    actually an alias for another name, and when Apache performs the
    address-to-name lookup it's getting the <EM>real</EM> name, not
    <SAMP>Host.FooBar.Com</SAMP>.  You can verify this by checking the
    reverse lookup yourself.  The easiest way to work around it is to
    specify the correct host name in your configuration.
   </LI>
   <LI><STRONG>Inadequate checking and verification in your
    configuration of Apache</STRONG>
    <BR>
    If you intend to perform access checking and restriction based upon
    the client's host or domain name, you really need to configure
    Apache to double-check the origin information it's supplied.  You do
    this by adding the <SAMP>-DMAXIMUM_DNS</SAMP> clause to the
    <SAMP>EXTRA_CFLAGS</SAMP> definition in your
    <SAMP>Configuration</SAMP> file.  For example:
    <P>
    <DL>
     <DD><CODE>EXTRA_CFLAGS=-DMAXIMUM_DNS</CODE>
     </DD>
    </DL>
    </P>
    <P>
    This will cause Apache to be very paranoid about making sure a
    particular host address is <EM>really</EM> assigned to the name it
    claims to be.  Note that this <EM>can</EM> incur a significant
    performance penalty, however, because of all the name resolution
    requests being sent to a nameserver.
    </P>
   </LI>
  </OL>
  <HR>
 </LI>
 <LI><A NAME="SSL-i">
      <STRONG>Why doesn't Apache include SSL?</STRONG>
     </A>
  <P>
  SSL (Secure Socket Layer) data transport requires encryption, and many
  governments have restrictions upon the import, export, and use of
  encryption technology.  If Apache included SSL in the base package,
  its distribution would involve all sorts of legal and bureaucratic
  issues, and it would no longer be freely available.  Also, some of
  the technology required to talk to current clients using SSL is
  patented by <A HREF="http://www.rsa.com/">RSA Data Security</A>,
  who restricts its use without a license.
  </P>
  <P>
  Some SSL implementations of Apache are available, however; see the
  &quot;<A
         HREF="http://www.apache.org/related_projects"
        >related projects</A>&quot;
  page at the main Apache web site.
  </P>
  <P>
  You can find out more about this topic in the <CITE>Apache Week</CITE>
  article about
  <A
   HREF="http://www.apacheweek.com/features/ssl"
   REL="Help"
  ><CITE>Apache and Secure Transactions</CITE></A>.
  </P>
  <HR>
 </LI>
 <LI><A NAME="HPUX-core">
       <STRONG>Why do I get core dumps under HPUX using HP's ANSI
               C compiler?</STRONG>
      </A>
  <P>
  We have had numerous reports of Apache dumping core when compiled
  with HP's ANSI C compiler using optimization.  Disabling the compiler
  optimization has fixed these problems.
  </P>
  <HR>
 </LI>
 <LI><A NAME="midi">
      <STRONG>How do I get Apache to send a MIDI file so the browser can
      play it?</STRONG>
     </A>
  <P>
  Even though the registered MIME type for MIDI files is
  <SAMP>audio/midi</SAMP>, some browsers are not set up to recognize it
  as such; instead, they look for <SAMP>audio/x-midi</SAMP>.  There are
  two things you can do to address this:
  </P>
  <OL>
   <LI>Configure your browser to treat documents of type
    <SAMP>audio/midi</SAMP> correctly.  This is the type that Apache
    sends by default.  This may not be workable, however, if you have
    many client installations to change, or if some or many of the
    clients are not under your control.
   </LI>
   <LI>Instruct Apache to send a different <SAMP>Content-type</SAMP>
    header for these files by adding the following line to your server's
    configuration files:
    <P>
    <DL>
     <DD><CODE>AddType audio/x-midi .mid .midi .kar</CODE>
     </DD>
    </DL>
    </P>
    <P>
    Note that this may break browsers that <EM>do</EM> recognize the
    <SAMP>audio/midi</SAMP> MIME type unless they're prepared to also
    handle <SAMP>audio/x-midi</SAMP> the same way.
    </P>
   </LI>
  </OL>
  <HR>
 </LI>
 <LI><A NAME="cantbuild">
       <STRONG>Why won't Apache compile with my system's
       <SAMP>cc</SAMP>?</STRONG>
     </A>
  <P>
  If the server won't compile on your system, it is probably due to one
  of the following causes:
  </P>
  <UL>
   <LI><STRONG>The <SAMP>Configure</SAMP> script doesn't recognize your system
    environment.</STRONG>
    <BR>
    This might be either because it's completely unknown or because
    the specific environment (include files, OS version, <EM>et
    cetera</EM>) isn't explicitly handled.  If this happens, you may
    need to port the server to your OS yourself.
   </LI>
   <LI><STRONG>Your system's C compiler is garbage.</STRONG>
    <BR>
    Some operating systems include a default C compiler that is either
    not ANSI C-compliant or suffers from other deficiencies.  The usual
    recommendation in cases like this is to acquire, install, and use
    <SAMP>gcc</SAMP>.
   </LI>
   <LI><STRONG>Your <SAMP>include</SAMP> files may be confused.</STRONG>
    <BR>
    In some cases, we have found that a compiler installation or system
    upgrade has left the C header files in an inconsistent state.  Make
    sure that your include directory tree is in sync with the compiler and
    the operating system.
   </LI>
   <LI><STRONG>Your operating system or compiler may be out of
    revision.</STRONG>
    <BR>
    Software vendors (including those that develop operating systems)
    issue new releases for a reason; sometimes to add functionality, but
    more often to fix bugs that have been discovered.  Try upgrading
    your compiler and/or your operating system.
   </LI>
  </UL>
  <P>
  The Apache Group tests the ability to build the server on many
  different platforms.  Unfortunately, we can't test all of the OS
  platforms there are.  If you have verified that none of the above
  issues is the cause of your problem, and it hasn't been reported
  before, please submit a
  <A
   HREF="http://www.apache.org/bugdb.cgi"
  >problem report</A>.
  Be sure to include <EM>complete</EM> details, such as the compiler
  &amp; OS versions and exact error messages.
  </P>
  <HR>
 </LI>
 <LI><A NAME="addlog">
      <STRONG>How do I add browsers and referrers to my logs?</STRONG>
     </A>
  <P>
  Apache provides a couple of different ways of doing this.  The
  recommended method is to compile the
  <A
   HREF="../mod/mod_log_config.html"
  ><SAMP>mod_log_config</SAMP></A>
  module into your configuration and use the
  <A
   HREF="../mod/mod_log_config.html#customlog"
  ><SAMP>CustomLog</SAMP></A>
  directive.
  </P>
  <P>
  You can either log the additional information in files other than your
  normal transfer log, or you can add them to the records already being
  written.  For example:
  </P>
  <P>
  <CODE>
   CustomLog&nbsp;logs/access_log&nbsp;"%h&nbsp;%l&nbsp;%u&nbsp;%t&nbsp;\"%r\"&nbsp;%s&nbsp;%b&nbsp;\"%{Referer}i\"&nbsp;\"%{User-Agent}i\""
  </CODE>
  </P>
  <P>
  This will add the values of the <SAMP>User-agent:</SAMP> and
  <SAMP>Referer:</SAMP> headers, which indicate the client and the
  referring page, respectively, to the end of each line in the access
  log.
  </P>
  <P>
  You may want to check out the <CITE>Apache Week</CITE> article
  entitled:
  &quot;<A
         HREF="http://www.apacheweek.com/features/logfiles"
         REL="Help"
        ><CITE>Gathering Visitor Information: Customising Your
         Logfiles</CITE></A>&quot;.
  </P>
  <HR>
 </LI>
 <LI><A NAME="bind8.1">
      <STRONG>Why do I get an error about an undefined reference to
      &quot;<SAMP>__inet_ntoa</SAMP>&quot; or other
      <SAMP>__inet_*</SAMP> symbols?</STRONG>
     </A>
  <P>
  If you have installed <A HREF="http://www.isc.org/bind.html">BIND-8</A>
  then this is normally due to a conflict between your include files
  and your libraries.  BIND-8 installs its include files and libraries
  <CODE>/usr/local/include/</CODE> and <CODE>/usr/local/lib/</CODE>, while
  the resolver that comes with your system is probably installed in
  <CODE>/usr/include/</CODE> and <CODE>/usr/lib/</CODE>.  If
  your system uses the header files in <CODE>/usr/local/include/</CODE>
  before those in <CODE>/usr/include/</CODE> but you do not use the new
  resolver library, then the two versions will conflict.
  </P>
  <P>
  To resolve this, you can either make sure you use the include files
  and libraries that came with your system or make sure to use the
  new include files and libraries.  Adding <CODE>-lbind</CODE> to the
  <CODE>EXTRA_LDFLAGS</CODE> line in your <SAMP>Configuration</SAMP>
  file, then re-running <SAMP>Configure</SAMP>, should resolve the
  problem.  (Apache versions 1.2.* and earlier use
  <CODE>EXTRA_LFLAGS</CODE> instead.)
  </P>
  <P>
  <STRONG>Note:</STRONG>As of BIND 8.1.1, the bind libraries and files are
  installed under <SAMP>/usr/local/bind</SAMP> by default, so you
  should not run into this problem.  Should you want to use the bind
  resolvers you'll have to add the following to the respective lines:
  </P>
  <P>
  <DL>
   <DD><CODE>EXTRA_CFLAGS=-I/usr/local/bind/include
    <BR>
    EXTRA_LDFLAGS=-L/usr/local/bind/lib
    <BR>
    EXTRA_LIBS=-lbind</CODE>
   </DD>
  </DL>
  </P>
  <HR>
 </LI>
 <LI><A NAME="set-servername">
      <STRONG>Why does accessing directories only work when I include
      the trailing "/"
      (<EM>e.g.</EM>,&nbsp;<SAMP>http://foo.domain.com/~user/</SAMP>)
      but not when I omit it
      (<EM>e.g.</EM>,&nbsp;<SAMP>http://foo.domain.com/~user</SAMP>)?</STRONG>
     </A>
  <P>
  When you access a directory without a trailing "/", Apache needs
  to send what is called a redirect to the client to tell it to
  add the trailing slash.  If it did not do so, relative URLs would
  not work properly.  When it sends the redirect, it needs to know
  the name of the server so that it can include it in the redirect.
  There are two ways for Apache to find this out; either it can guess,
  or you can tell it.  If your DNS is configured correctly, it can
  normally guess without any problems.  If it is not, however, then
  you need to tell it.
  </P>
  <P>
  Add a <A HREF="../mod/core.html#servername">ServerName</A> directive
  to the config file to tell it what the domain name of the server is.
  </P>
  <HR>
 </LI>
 <LI><A NAME="user-authentication">
      <STRONG>How do I set up Apache to require a username and
      password to access certain documents?</STRONG>
     </A>
  <P>
  There are several ways to do this; some of the more popular
  ones are to use the <A HREF="../mod/mod_auth.html">mod_auth</A>,
  <A HREF="../mod/mod_auth_db.html">mod_auth_db</A>, or
  <A HREF="../mod/mod_auth_dbm.html">mod_auth_dbm</A> modules.
  </P>
  <P>
  For an explanation on how to implement these restrictions, see
  <A
   HREF="http://www.apacheweek.com/"
  ><CITE>Apache Week</CITE></A>'s
  articles on
  <A
   HREF="http://www.apacheweek.com/features/userauth"
  ><CITE>Using User Authentication</CITE></A>
  or
  <A
   HREF="http://www.apacheweek.com/features/dbmauth"
  ><CITE>DBM User Authentication</CITE></A>.
  </P>
  <HR>
 </LI>
 <LI><A NAME="remote-user-var">
         <STRONG>Why is the environment variable 
         <SAMP>REMOTE_USER</SAMP> not set?</STRONG>
         </A>
  <P>
  This variable is set and thus available in SSI or CGI scripts <STRONG>if and
  only if</STRONG> the requested document was protected by access
  authentication.  For an explanation on how to implement these restrictions,
  see
  <A
   HREF="http://www.apacheweek.com/"
  ><CITE>Apache Week</CITE></A>'s
  articles on
  <A
   HREF="http://www.apacheweek.com/features/userauth"
  ><CITE>Using User Authentication</CITE></A>
  or
  <A
   HREF="http://www.apacheweek.com/features/dbmauth"
  ><CITE>DBM User Authentication</CITE></A>.
  </P>
  <P>
  Hint: When using a CGI script to receive the data of a HTML <SAMP>FORM</SAMP>
  notice that protecting the document containing the <SAMP>FORM</SAMP> is not
  sufficient to provide <SAMP>REMOTE_USER</SAMP> to the CGI script.  You have
  to protect the CGI script, too. Or alternatively only the CGI script (then
  authentication happens only after filling out the form).
  </P>
  <HR>
 </LI>
 <LI><A NAME="remote-auth-only">
      <STRONG>How do I set up Apache to allow access to certain
      documents only if a site is either a local site <EM>or</EM>
      the user supplies a password and username?</STRONG>
     </A>
  <P>
  Use the <A HREF="../mod/core.html#satisfy">Satisfy</A> directive,
  in particular the <CODE>Satisfy Any</CODE> directive, to require
  that only one of the access restrictions be met.  For example,
  adding the following configuration to a <SAMP>.htaccess</SAMP>
  or server configuration file would restrict access to people who
  either are accessing the site from a host under domain.com or
  who can supply a valid username and password:
  </P>
  <P>
  <DL>
   <DD><CODE>deny from all
    <BR>
    allow from .domain.com
    <BR>
    AuthType Basic
    <BR>
    AuthUserFile /usr/local/etc/httpd/conf/htpasswd.users
    <BR>
    AuthName special directory
    <BR>
    require valid-user
    <BR>
    satisfy any</CODE>
   </DD>
  </DL>
  </P>
  <P>
  See the <A HREF="#user-authentication">user authentication</A>
  question and the <A HREF="../mod/mod_access.html">mod_access</A>
  module for details on how the above directives work.
  </P>
  <HR>
 </LI>
 <LI><A NAME="no-info-directives">
      <STRONG>Why doesn't mod_info list any directives?</STRONG>
     </A>
  <P>
  The
  <A
   HREF="../mod/mod_info.html"
  ><SAMP>mod_info</SAMP></A>
  module allows you to use a Web browser to see how your server is
  configured.  Among the information it displays is the list modules and
  their configuration directives.  The &quot;current&quot; values for
  the directives are not necessarily those of the running server; they
  are extracted from the configuration files themselves at the time of
  the request.  If the files have been changed since the server was last
  reloaded, the display will will not match the values actively in use.
  If the files and the path to the files are not readable by the user as
  which the server is running (see the
  <A
   HREF="../mod/core.html#user"
  ><SAMP>User</SAMP></A>
  directive), then <SAMP>mod_info</SAMP> cannot read them in order to
  list their values.  An entry <EM>will</EM> be made in the error log in
  this event, however.
  </P>
  <HR>
 </LI>
 <LI><A NAME="linux-shmget">
      <STRONG>When I run it under Linux I get "shmget:
      function not found", what should I do?</STRONG>
     </A>
  <P>
  Your kernel has been built without SysV IPC support.  You will have to
  rebuild the kernel with that support enabled (it's under the
  &quot;General Setup&quot; submenu).  Documentation for
  kernel building is beyond the scope of this FAQ; you should consult
  the
  <A HREF="http://www.linuxhq.com/HOWTO/Kernel-HOWTO.html"
  >Kernel HOWTO</A>,
  or the documentation provided with your distribution, or a
  <A HREF="http://www.linuxhq.com/HOWTO/META-FAQ.html"
  >Linux newsgroup/mailing list</A>.
  As a last-resort workaround, you can
  comment out the <CODE>#define HAVE_SHMGET</CODE> definition in the
  <SAMP>LINUX</SAMP> section of
  <SAMP>src/conf.h</SAMP> and rebuild the server.  This will produce
  a server which is slower and less reliable.
  </P>
  <HR>
 </LI>
 <LI><A NAME="authauthoritative">
      <STRONG>Why does my authentication give me a server error?</STRONG>
     </A>
  <P>
  Under normal circumstances, the Apache access control modules will
  pass unrecognized user IDs on to the next access control module in
  line.  Only if the user ID is recognized and the password is validated
  (or not) will it give the usual success or &quot;authentication
  failed&quot; messages.
  </P>
  <P>
  However, if the last access module in line 'declines' the validation
  request (because it has never heard of the user ID or because it is not
  configured), the <SAMP>http_request</SAMP> handler will give one of
  the following, confusing, errors:
  </P>
  <UL>
   <LI><SAMP>check access</SAMP>
   </LI>
   <LI><SAMP>check user.  No user file?</SAMP>
   </LI>
   <LI><SAMP>check access.  No groups file?</SAMP>
   </LI>
  </UL>
  <P>
  This does <EM>not</EM> mean that you have to add an
  '<SAMP>AuthUserFile&nbsp;/dev/null</SAMP>' line as some magazines suggest!
  </P>
  <P>
  The solution is to ensure that at least the last module is authoritative
  and <STRONG>CONFIGURED</STRONG>. By default, <SAMP>mod_auth</SAMP> is
  authoritative and will give an OK/Denied, but only if it is configured
  with the proper <SAMP>AuthUserFile</SAMP>.  Likewise, if a valid group
  is required.  (Remember that the modules are processed in the reverse
  order from that in which they appear in your compile-time
  <SAMP>Configuration</SAMP> file.)
  </P>
  <P>
  A typical situation for this error is when you are using the
  <SAMP>mod_auth_dbm</SAMP>, <SAMP>mod_auth_msql</SAMP>,
  <SAMP>mod_auth_mysql</SAMP>, <SAMP>mod_auth_anon</SAMP> or
  <SAMP>mod_auth_cookie</SAMP> modules on their own.  These are by
  default <STRONG>not</STRONG> authoritative, and this will pass the
  buck on to the (non-existent) next authentication module when the
  user ID is not in their respective database.  Just add the appropriate
  '<SAMP><EM>XXX</EM>Authoritative yes</SAMP>' line to the configuration.
  </P>
  <P>
  In general it is a good idea (though not terribly efficient) to have the
  file-based <SAMP>mod_auth</SAMP> a module of last resort. This allows
  you to access the web server with a few special passwords even if the
  databases are down or corrupted.  This does cost a
  file open/seek/close for each request in a protected area.
  </P>
  <HR>
 </LI>
 <LI><A NAME="auth-on-same-machine">
      <STRONG>Do I have to keep the (mSQL) authentication information
      on the same machine?</STRONG>
     </A>
  <P>
  Some organizations feel very strongly about keeping the authentication
  information on a different machine than the webserver. With the
  <SAMP>mod_auth_msql</SAMP>, <SAMP>mod_auth_mysql</SAMP>, and other SQL
  modules connecting to (R)DBMses this is quite possible. Just configure
  an explicit host to contact.
  </P>
  <P>
  Be aware that with mSQL and Oracle, opening and closing these database
  connections is very expensive and time consuming. You might want to
  look at the code in the <SAMP>auth_*</SAMP> modules and play with the
  compile time flags to alleviate this somewhat, if your RDBMS licences
  allow for it.
  </P>
  <HR>
 </LI>
 <LI><A NAME="msql-slow">
      <STRONG>Why is my mSQL authentication terribly slow?</STRONG>
     </A>
  <P>
  You have probably configured the Host by specifying a FQHN,
  and thus the libmsql will use a full blown tcp/ip socket to talk to
  the database, rather than a fast internal device.  The
  <SAMP>libmsql</SAMP>, the mSQL FAQ, and the <SAMP>mod_auth_msql</SAMP>
  documentation warn you about this.  If you have to use different
  hosts, check out the <SAMP>mod_auth_msql</SAMP> code for
  some compile time flags which might - or might not - suit you.
  </P>
  <HR>
 </LI>
 <LI><A NAME="rewrite-more-config">
          <STRONG>Where can I find mod_rewrite rulesets which already solve
          particular URL-related problems?</STRONG>
     </A>
  <P>
  There is a collection of 
  <A
      HREF="http://www.engelschall.com/sw/mod_rewrite/docs/mod_rewrite/solutions.html#Solutions"
  >Practical Solutions for URL-Manipulation</A>
  where you can
  find all typical solutions the author of 
  <A
   HREF="../mod/mod_rewrite.html"
  ><SAMP>mod_rewrite</SAMP></A> 
  currently knows of. If you have more
  interesting rulesets which solve particular problems not currently covered in
  this document, send it to 
  <A
      HREF="mailto:rse@apache.org"
  >Ralf S. Engelschall</A>
  for inclusion. The
  other webmasters will thank you for avoiding the reinvention of the wheel.
  </P>
  <HR>
 </LI>
 <LI><A NAME="rewrite-article">
          <STRONG>Where can I find any published information about URL-manipulations and
          mod_rewrite?</STRONG>
     </A>
  <P>
  There is an article from 
  <A
      HREF="mailto:rse@apache.org"
  >Ralf S. Engelschall</A>
  about URL-manipulations based on
  <A
   HREF="../mod/mod_rewrite.html"
  ><SAMP>mod_rewrite</SAMP></A> 
  in the &quot;iX Multiuser Multitasking Magazin&quot; issue #12/96. The
  german (original) version
  can be read online at 
  <A
      HREF="http://www.heise.de/ix/artikel/9612149/"
  >http://www.heise.de/ix/artikel/9612149/</A>,
  the English (translated) version can be found at 
  <A
      HREF="http://www.heise.de/ix/artikel/E/9612149/"
  >http://www.heise.de/ix/artikel/E/9612149/</A>.
  </P>
  <HR>
 </LI>
 <LI><A NAME="rewrite-complexity">
          <STRONG>Why is mod_rewrite so difficult to learn and seems so
          complicated?</STRONG>
     </A>
  <P>
  Hmmm... there are a lot of reasons. First, mod_rewrite itself is a powerful
  module which can help you in really <b>all</b> aspects of URL rewriting, so
  it can be no trivial module per definition. To accomplish its hard job it
  uses software leverage and makes use of a powerful regular expression
  library by Henry Spencer which is an integral part of Apache since its
  version 1.2.  And regular expressions itself can be difficult to newbies,
  while providing the most flexible power to the advanced hacker. 
  </P>
  <P>
  On the other hand mod_rewrite has to work inside the Apache API environment
  and needs to do some tricks to fit there. For instance the Apache API as of
  1.x really was not designed for URL rewriting at the <tt>.htaccess</tt>
  level of processing. Or the problem of multiple rewrites in sequence, which
  is also not handled by the API per design. To provide this features
  mod_rewrite has to do some special (but API compliant!) handling which leads
  to difficult processing inside the Apache kernel. While the user usually
  doesn't see anything of this processing, it can be difficult to find
  problems when some of your RewriteRules seem not to work.
  </P>
  <HR>
 </LI>
 <LI><A NAME="rewrite-dontwork">
          <STRONG>What can I do if my RewriteRules don't work as expected?
          </STRONG>
     </A>
  <P>
  Use &quot;<SAMP>RewriteLog somefile</SAMP>&quot; and
  &quot;<SAMP>RewriteLogLevel 9</SAMP>&quot; and have a precise look at the
  steps the rewriting engine performs. This is really the only one and best
  way to debug your rewriting configuration.
  </P>
  <HR>
 </LI>
 <LI><A NAME="rewrite-prefixdocroot"><STRONG>Why don't some of my URLs
      get prefixed with DocumentRoot when using mod_rewrite?</STRONG>
     </A>
  <P>
  If the rule starts with <SAMP>/somedir/...</SAMP> make sure that really no
  <SAMP>/somedir</SAMP> exists on the filesystem if you don't want to lead the
  URL to match this directory, i.e. there must be no root directory named
  <SAMP>somedir</SAMP> on the filesystem. Because if there is such a
  directory, the URL will not get prefixed with DocumentRoot. This behaviour
  looks ugly, but is really important for some other aspects of URL
  rewriting.
  </P>
  <HR>
 </LI>
 <LI><A NAME="rewrite-nocase">
          <STRONG>How can I make all my URLs case-insensitive with mod_rewrite?
          </STRONG>
     </A>
  <P>
  You can't! The reason is: First, case translations for arbitrary length URLs
  cannot be done via regex patterns and corresponding substitutions. One need
  a per-character pattern like sed/Perl <SAMP>tr|..|..|</SAMP> feature.  Second, just
  making URLs always upper or lower case will not resolve the complete problem
  of case-INSENSITIVE URLs, because actually the URLs had to be rewritten to
  the correct case-variant residing on the filesystem because in later
  processing Apache needs to access the file.  And Unix filesystem is always
  case-SENSITIVE.
  </P>
  <P>
  But there is a module named <CODE>mod_speling.c</CODE> (yes, it is named
  this way!) out there on the net. Try this one.
  </P>
  <HR>
 </LI>
 <LI><A NAME="rewrite-virthost">
          <STRONG> Why are RewriteRules in my VirtualHost parts ignored?
          </STRONG>
     </A>
  <P>
  Because you have to enable the engine for every virtual host explicitly due
  to security concerns. Just add a &quot;RewriteEngine on&quot; to your
  virtual host configuration parts.
  </P>
  <HR>
 </LI>
 <LI><A NAME="rewrite-envwhitespace">
          <STRONG> How can I use strings with whitespaces in RewriteRule's ENV
          flag?</STRONG>
     </A>
  <P>
  There is only one ugly solution: You have to surround the complete flag
  argument by quotation marks (<SAMP>"[E=...]"</SAMP>). Notice: The argument
  to quote here is not the argument to the E-flag, it is the argument of the
  Apache config file parser, i.e. the third argument of the RewriteRule here.
  So you have to write <SAMP>"[E=any text with whitespaces]"</SAMP>.
  </P>
  <HR>
 </LI>
 <LI><A NAME="cgi-spec"><STRONG>Where can I find the &quot;CGI
      specification&quot;?</STRONG></A>
  <P>
  The Common Gateway Interface (CGI) specification currently lives in at
  least two versions:
  </P>
  <P>
  <OL>
   <LI>At the original NCSA site
    &lt;<A
         HREF="http://hoohoo.ncsa.uiuc.edu/cgi/interface.html"
        ><SAMP>http://hoohoo.ncsa.uiuc.edu/cgi/interface.html</SAMP></A>&gt;.
    This version hasn't been updated since 1995, and there have been
    some efforts to update it and replace it with
   </LI>
   <LI>The most current version, which is struggling to become an
    Internet RFC, found at
    &lt;<A
         HREF="http://www.ast.cam.ac.uk/~drtr/cgi-spec.html"
        ><SAMP>http://www.ast.cam.ac.uk/~drtr/cgi-spec.html</SAMP></A>&gt;.
   </LI>
  </OL>
  </P>
  <HR>
 </LI>

  <!-- Don't forget to add HR tags at the end of each list item.. -->

</OL>
 <!--#include virtual="footer.html" -->
</BODY>
</HTML>
